circle circular coast dais disc emergency helicopter landing pad helipad landing landing pad madeira plinth sea communicating communication display displayed ground helicopter landing-pad landing-spot mark marked transport visual air first aid rescue building clear cleared development empty fences foundation work foundations groundwork land level levelling levels property ready for building sand sand pads suburban urban vacant vacant block foundation-work leveling ready-for-building sand-pads vacant-block bricks construction fencing preparation real estate solid wall